June 20, 2016
Ionic 2 use NavController in Service to show Alerts
Usually you inject Nav:NavController into your classes constructor to use it:
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constructor(private Nav:NavController) {} |
But if you are working in a service you will receive the following error:
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No provider for NavController! (ExampleService -> NavController) |
If you want to show alerts from within a service you are required to use the NavController. To do so simply create the private field nav with type NavController. Then use the app.getActiveNav method provided by ionic-angular. See the snippet below for a full example:
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import {Injectable} from '@angular/core'; import {NavController, App} from "ionic-angular/index"; import {SetDetailPage} from "../../pages/set-detail-page"; @Injectable() export class ExampleService { private nav:NavController; constructor(private app:App) { this.nav = app.getActiveNav(); } showAlert() { this.nav.present({ ... }) } } |
Now you can show dialogs and alerts from a service in Ionic 2. But keep in mind, this is not good practice – services should not be tied to the UI of your application.
Admin Admin
Developer at 
Please can we get the javascript version?? it keeps giving no provider for App!!
Hello Alugbin Abiodun,
first of all – developing a Ionic 2 app with JavaScript is a BIG mistake. Take 3 days to learn the necessary TypeScript it will save you way more time.
However you should be able to use app.getActiveNav(); in JavaScript as well, just follow the imports in the code snippet. I couldn’t setup a JavaScript App with ionic since the startup repositories are now fully in TypeScript.
Hi there!
This blog post was very helpful!
I have an ErrorService that I was using to catch errors thorough the application and display an alert. I know that this is bad practice (as stated by many other blogs as well) but I have never seen a good example of error handling and display?
Where should the error UI (AlertController and such) go? How could you set up a global error class to be reusable between all components, if that’s even possible.
Thanks so much for your help!
The nav.present method I do not see in the ionic2 now. was that removed?
Can you please explain any other way I can do that?
Hello,
as you can see in the changelog the method was moved from the nav to the overlay instance (e.g. modal, alert).
https://github.com/driftyco/ionic/blob/master/CHANGELOG.md#200-beta11-2016-08-05
So the usage is now:
let alert = this.alertCtrl.create({
title: ‘Alert’
});
alert.present();
Thanks man, it worked here!
Thank you great explanation!
Thank you so much! This is solution for my problem!
Thank you for the useful update For beginners and start your career in Ionic.
Thanks for giving error and nav controller code. These code are usefull ionic developer.
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